PHILADELPHIA -- Archaeologists have uncovered what they say they believe are the remains of Irish immigrants in a mass grave some 20 miles west of Philadelphia.

The team based at Immaculata University discovered the grave with 90 human bones while researching the mysterious deaths of 57 Irish men who arrived in Pennsylvania to work on the railroad in 1832 and died eight weeks later, the Philadelphia Inquirer reported Wednesday.

A secret file on the missing men piqued the interest of two brothers, both historians, who decided to find out exactly what happened to the immigrants.

The Rev. Frank Watson and his twin brother, William, gathered several of William's colleagues from Immaculata and began searching for the gravesite using clues from the secret file.

Their discovery was announced Tuesday.

Before finding the mass grave, the researchers dug up several thousand artifacts from a shanty town where immigrants lived.